1. Field of the Invention
This invention relates generally to hypodermic injection devices, and more particularly to a single use needleless injection device that utilizes a fine high pressure stream of the liquid medicament to penetrate the skin and deliver the desired dosage into a patient's body.
2. Description of Related Information
The needleless jet injection art dates from the 1940's. The ability to perform needleless hypodermic penetrations developed as a result of observations of accidental injection of fluids into workers handling high pressure hydraulic lines having pinhole leaks.
The resultant early jet injector devices actually commercialized tended toward being large, complex units generally adapted to retain sufficient quantities of medicament for repeated injections. Most of these devices were intended for usage in fixed site situations such as army induction centers or mass inoculations at clinics.
Smaller portable devices also have been developed which are powered by compressed gas or springs. For the most part, these devices are complex and multi-component as well as requiring dismantling, reassembly and sterilization between uses.
Attempts have been made to simplify the usage of needleless injectors and make them more practical for individuals required to self-administer medicaments. Several devices have been developed with single use cartridges containing a liquid medicament intended for use with a reusable driver mechanism. Representative of these are U.S. Pat. No. 4,874,367 which teaches a single use cartridge and a reusable spring powered driver mechanism and U.S. Pat. No. 4,941,880 which teaches a prefilled medicament ampule with a reusable compressed gas powered drive mechanism. The devices taught in the '367 and '880 patents are complex and multi-component. They have a mass and size similar to a two cell "C" flashlight.
A single use device employing a gas powered drive mechanism is taught in U.S. Pat. No. 5,009,637. The teachings describe a threaded socket for a filled vial to vary the dose delivered. The '637 device has numerous parts and requires a fracturable high pressure cylinder or ampule to contain the compressed gas.
Size and complexity of the drive mechanism has largely precluded the use of needleless injectors for stand-by self administration of medicaments for acute insect bite allergy reactions, migraine attacks, infertility, impotence and the like. The majority of the devices in the prior art are designed to be reusable, hence they must be reloadable, thereby increasing their physical complexity and mass. As a result, most stand-by self administration kits currently available use either prefilled hypodermic syringes, or sealed ampules and a standard hypodermic syringe. While these kits are satisfactory for their intended use, in many states possession and disposal of syringes is regulated, thereby affecting their availability and use. Further, self administration of an injectable medicament, either with a prefilled syringe or a sealed ampule with a standard syringe, particularly under conditions of a physical stress such as an allergy or migraine attack requires a high level of control and skill on the part of the patient. A single use prefilled needleless hypodermic injection device which was simple to use, not complex to manufacture, hence available at a reasonable cost, designed not to be reuseable, thus likely not subject to the regulatory requirements regarding possession and disposal of hypodermic syringes, would represent an advance to the art. Such a device is described hereinbelow.